Tumor necrosis factor induces activation of mitochondrial succinate dehydrogenase.

We have studied TNF-induced changes in mitochondrial enzymes. One enzyme, succinate dehydrogenase (SDH), is specifically activated in TNF sensitive cells including U937 (human monocytic), WEHI-164 (murine fibrosarcoma), and ME-180 (human cervical carcinoma). SDH is activated by TNF concentrations which also cause cytolysis, however the enzyme activity is elevated several hours before maximum cytotoxicity is observed. In contrast, TNF does not activate SDH in TNF resistant variants derived from U937 and WEHI-164.